Conventional disk drive apparatus of the type disclosed in FIG. 21, that are built-in or connected with equipment such as computers. In FIG. 21, the disk drive apparatus has a chassis 2 made of a die cast Aluminum. A spindle motor 9 is mounted on a rear surface of the chassis 2. Dual sided disks 3 are driven by the spindle motor 9 to rotate at a constant angular velocity (CAV).
An arm 4 is mounted on the chassis 2 so as to be pivotal around a perpendicular axis 4a. At one end of this arm, a voice coil 5 is mounted while at a second end thereof, a slider 6 is mounted.
On the chassis 2, magnets 7a and 7b are mounted so as to face with voice coil 5. A voice coil motor 7 comprises the voice coil 5 and the magnets 7a and 7b. When an electric current is supplied to the voice coil 5, the arm 4 rotates around the perpendicular axis 4 by means of the force caused between the magnetic field from the magnet 7a and 7b and the electric current supplied to this voice coil 5. By this force, the slider 6 at the second end of the arm 4 moves in a substantially radial direction of the magnetic disk 3 as shown by an arrow X in FIG. 22.
Therefore, a magnetic head 8 fixed to this slider 6 in the manner shown in FIG. 13 performs a SEEK operation to the magnetic disk 3. Thus, recording and reproducing information can be performed on selected tracks of the magnetic disk 3. This slider 6 is constructed as shown in FIG. 23. In other words, rails 6a and 6b which are formed at both ends of a bottom surface of the slider 6, cooperate to form an air bearing surface. Tapered portions 6c and 6d are formed on these rails 6a and 6b at an air entrance end.
By means of these tapered rails, air flow is generated between a surface of the magnetic disk 3 and the rails 6a and 6b of slider 6 as the magnetic disk rotates. Therefore, when the slider 6 accesses the rotating magnetic disk 3, the slider is provided with a supportive "flying" force.
By this flying force, the slider 6 and the magnetic head 8 mounted thereon float a small distance above a surface of the magnetic disk 3. Since there is no direct contact between the magnetic head 8 and a surface of magnetic disk 3, abrasion and damage of the magnetic disk 3 can be avoided.
By constructing this flying type head slider 6 as described above, the floating distance (d) of the magnetic head 8 from the magnetic disk 3 can be maintained constant for each track, even though the magnetic disk 3 has a "bumpy" surface as shown in FIG. 24.
When the magnetic disk 3 rotates at a constant angular velocity with the above flying type head slider 6, the linear velocity at outer periphery is higher than that at an inner periphery. Therefore, this causes a problem that the floating distance (d) of the slider 6 exhibits a relatively large variation depending on whether the slider 6 is located at the outer periphery or the inner periphery of the magnetic disk 3.
When the arm 4 rotates around the perpendicular axis 4a, the slider 6 moves through an arc, and not along a straight line as it moves in a radial direction towards the center of the magnetic disk 3, as shown in FIG. 25. Therefore, as shown in FIG. 26, a center line 6e of this slider 6 becomes offset with respect to a tangential line of a track 3a. This causes the skew angle .theta.s. The skew angle .theta.s varies depending on the distance from the center of magnetic disk 3.
The flying force acting on the slider 6 also varies as the skew angle varies by means of the air flow generated between the surface of magnetic disk 3 and the rails 6a and 6b of the slider 6 as the magnetic disk 3 rotates. Once the floating distance (d) varies depending on the skew angle .theta.s, it causes a problem that accurate recording and reproducing can not be performed on desired tracks.
An improvement has been proposed such disclosed in U.S. Pat. No. 4,894,740 in which three rails are formed on the bottom surface of the slider. A wall or walls of a rail which is faced with another wall of another rail is tapered or flared so as to resolve the above problem. However, even with this arrangement a stabilized floating height could not be satisfactorily obtained.